Inertia-sensitive device

Abstract

An inertia-sensitive device for detecting movement of, or impact on, the device or vibrations in its vicinity comprises a housing having a flat or concave surface, a ball freely supported within the housing upon that surface, the ball and/or the surface having an uneven texture, and a piezoelectric detector in direct or indirect contact with said housing. In one form of the device, which is illustrated, the surface is roughened and extends to a full spherical surface and the ball is of steel.

I claim: 
     
       1. An inertia-sensitive device for detecting movement, impact or vibrations, comprising: (a) a closed housing made of a molded rigid synthetic plastics material;   (b) said housing having molded therein a spherical concave uneven surface;   (c) a metal ball supported within said housing upon said spherical surface;   (d) the radius of said ball being not less than one twentieth of the radius of said spherical surface;   (e) a generally tubular extension formed integral with said housing and projecting therefrom to an end portion, whereby to constitute a support for said housing;   (f) piezoelectric detector means secured across the end portion of said generally tubular extension remote from said housing; and   (g) said piezoelectric detector means comprising a thin sheet of piezoelectric material having a peripheral edge portion, said piezoelectric material being supported on said tubular extension only at said peripheral edge portion.   
     
     
       2. An inertia-sensitive device according to claim 1 wherein said generally tubular extension is a cylindrical extension. 
     
     
       3. An inertia-sensitive device according to claim 2 wherein the radius of said metal ball is not less than one fifth of the radius of said spherical surface. 
     
     
       4. An inertia-sensitive device according to claim 3 wherein said metal ball is made of steel. 
     
     
       5. An inertia-sensitive device according to claim 2 wherein said cylindrical extension encompasses said piezoelectric detector. 
     
     
       6. An inertia-sensitive device according to claim 5 wherein said cylindrical extension further encompasses a portion of said closed housing.